A Study On The Local Scour Characteristics Around Pier Under Ice Cover And The Anti-Scour Structure Optimization

The paper is a research on the Pier Scour Characteristics under ice cover and the Optimized effect of the ring-wing scour plates under large-trolleying discharge. The experiment under ice cover mainly studied the change of velocity distribution law, discharge capacity, velocity near bed in front of pier, and local scour pit. The anti-scour structure optimization experiment formed a multi-level structure by increasing scour plates on the base of the single scour plate. The conclusions include:(1)The cover makes velocity distribution law change, and makes discharge capacity reduce.(2) The moving velocity near bed in front of pier under ice cover is a little more than that in open channel, and the vertical velocity near bed in front of pier under ice cover is obviously less than that in open channel. Also, the lengths, widths, depths and volumes of local scour pits under ice cover are smaller than those in open channel. Therefore, the ice cover has no adverse influence on local scour around piers.(3)The paper did a principal component analysis on anti-scour indexes by multivariate statistical methods. It has proved first principal component can be alone seen as max pit depths. In addition, the paper analyzed the anti-scour effect using max pit depths.(4)The anti-scour effect can’t be improved by increasing scour plates at 0.021m3/s, but it can be increased at 0.032m3/s and 0.042 m3/s. Besides, the anti-scour effect increases with decrease of the spacings between scour plates, and enhances with increase of the outer diameters of scour plates. However, the anti-scour effect of three scour plates is similar to that of two scour plates. The ratio of scour plate outer diameter and pier diameter is two to one. The third-level scour plate has little effect on experimental results. Therefore, the optimized structure of the ring-wing anti-scour Plates will be two slices of anti-scour plates. The outer diameters of anti-scour plates are 180mm, and the spacing between anti-scour plates is 15mm.(5) The ring-wing scour Plates has no grat influence on turbulence widths, this is a reasonable anti-scour structure from the perspective of navigation safety...